Magnetostratigraphy and correlation of Miocene basalts of the northern Oregon coast and Columbia plateau, southeast Washington.

Abstract

Paleomagnetic measurements are used to supplement other technqiues in an attempt to resolve stratigraphic problems in the Columbia River Basalt Group of the Columbia Plateau in southeast Washington and in basalts exposed along the northern Oregon coast. During the middle and late Miocene, the coastal and plateau basalts were erupted from separate sources hundreds of kilometers apart. We have collected 384 oriented cores from 63 sites for purposes of developing the magnetostratigraphy and determining the temporal relationships of the coastal basalts with stratigraphy and determining the temporal relationships of the coastal basalts with those exposed on the Columbia Plateau. This survey studied dikes and flows from members of the Saddle Mountains, Wanapum, and Grande Ronde Basalts of the Yakima Basalt Subgroup on the plateau and from the Cape Foulweather and Depoe Bay Basalts of the Oregon coast. -Authors